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CV jointed shafts , a question


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As we are talkink about hints besides my idea milling the bearing housing

or make a new housing from steel it might be possible to machine the hub

at another position.

 

I do not know if there is enough material, but worth a look at:

Inside where the big bearing sits the hub has a flange where the bearing is bolted to.

this flange can be cut 1,5mm to allow the bearing to slide more,

The closest point might be the hole from opposite side to allow the centre nut to be fixed.

if there still is a convenient amoint of material remaining, so why not?

 

Eventually the end of the tube area has to be cut also this 1,5mm

that the cv-joint still spanns the bearing together.

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Hi Stuart,

not sure what would need machining to fit or why but be careful.

A couple of years ago one of the main TR garages (I'm sure it was Revington) had to sort out a CV shaft (not one of theirs) that had burst through the hub - shaft longer than space available.

 

The kit (or the query) should be sent back to the supplier/manufacturer for their comment.

 

Roger

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Hi Roger, I would expect that that shaft was too short, not to long.

 

We are talking about few milimetres to travel in length totally and even in

very, very few millimetres in difference what diff and hub flange distances differ.

Reasons can be weldings on the frame or strange setup with the shims.

 

If too long this will let the axle press outside when wheels are close to lower bumpstop.

All in all mostly a very small distance that will be accepted in the rubber bushings

maybe with strange driving behaviour but not with something to brake.

This misalignment is easy to detect when the axle is fitted.

 

My bet would be that axle was to short what is not noticed under normal driving conditions.

When driving over an obstacle the wheel can be pushed to the upper bumpstop and the

full way to travel of the cv-shaft is requiered.

 

If that is not enough the toothed end of the shaft is pushed out of the inner part of the cv-joint.

It is secured with a ring offering limited resistance against separation for inspection or renewing.

 

This pushed out shaft will have turned the inner part of the cv-joint, prohibiting that the shaft

can slide back where ist belongs. Than the wheels comes downward putting force on the shaft

until something brakes because the shaft now is much longer due to the mistake in the toothed end.

 

All that trouble started with ignoring the fitting instructions

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Hi Roger, I would expect that that shaft was too short, not to long.

 

We are talking about few milimetres to travel in length totally and even in

very, very few millimetres in difference what diff and hub flange distances differ.

Reasons can be weldings on the frame or strange setup with the shims.

 

If too long this will let the axle press outside when wheels are close to lower bumpstop.

All in all mostly a very small distance that will be accepted in the rubber bushings

maybe with strange driving behaviour but not with something to brake.

This misalignment is easy to detect when the axle is fitted.

 

My bet would be that axle was to short what is not noticed under normal driving conditions.

When driving over an obstacle the wheel can be pushed to the upper bumpstop and the

full way to travel of the cv-shaft is requiered.

 

If that is not enough the toothed end of the shaft is pushed out of the inner part of the cv-joint.

It is secured with a ring offering limited resistance against separation for inspection or renewing.

 

This pushed out shaft will have turned the inner part of the cv-joint, prohibiting that the shaft

can slide back where ist belongs. Than the wheels comes downward putting force on the shaft

until something brakes because the shaft now is much longer due to the mistake in the toothed end.

 

All that trouble started with ignoring the fitting instructions

No as Roger said shaft too long.

Stuart.

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Hi Chris,

you can get the same effect if you fit longer rear springs in order to increase ground clearance.

 

There is not a lot of leeway around the drive shafts.

 

Roger

It was mentioned to me that the acceptable dimensions would not be exceeded with a standard car fitted with lever arm shocks. I guess once a car is away from standard the onus is on the owner to ensure additional items fitted are suitable for the application at the minimum by checking with the supplier.

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Need to do some measurements but I suspect the shoes would with the extra width now be running on the very inside of the drum.

Stuart.

Stuart, as the back plate goes behind the hub flange then the brake shoes must be in the correct position and therefore can I ask does the whole hub stick out further or is it just the wheel flange which is thicker which would hold the drum away from the shoes making them run closer to the outer ( open ) edge.

Chris

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Stuart, as the back plate goes behind the hub flange then the brake shoes must be in the correct position and therefore can I ask does the whole hub stick out further or is it just the wheel flange which is thicker which would hold the drum away from the shoes making them run closer to the outer ( open ) edge.

Chris

As I said earlier the hub is 1/32" thicker and the flange is 1/32" thicker too thus putting the drum further out. The backplate is still in its original position.

Stuart.

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It was mentioned to me that the acceptable dimensions would not be exceeded with a standard car fitted with lever arm shocks. I guess once a car is away from standard the onus is on the owner to ensure additional items fitted are suitable for the application at the minimum by checking with the supplier.

 

Yes, as the movement of the shifting element in the cv-joint is not endless

the shaft length must fit to suit.

 

I think its a normal process when buying trousers to look if they fit.

If not they have to be shortened or lengthened.

Even the crank gets this procedure or the shafts in the gearbox!

 

That easy procedure should be accepted for our cars especially when there

is a leaflet with a detailed instruction and recommendation how to proceed

coming with the shafts and everybody knows that the are shims at the rear axle

that change required shaft length.

I wonder how many complains I found related to that simple problem.

-Just as much as referring to correct travel way of rear telescopic dampers-

Measuring seems to be a myth.........

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I measured the original hub against the CDD hub and to avoid any confusion here is what I measured

 

post-754-0-41617000-1487341912_thumb.jpg

 

Without any doubt the CDD hub will position the drum further away from the shoes and the brake plate, but depending on the drum it might still be in limits

Edited by jean
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So, two different items under discussion here,

1.

Thickness of wheel flange and hub having a slight affect on postion of brake drum over shoes.

 

2. Length of driveshaft and effect of excessive up/Down movement of swinging arm on durability of CV shaft assy.

Item 1. Could impact on durability/ life of brake shoes if drum has wear ridges and is not smoothe.

 

Item 2. In extreeme circumstances where the movement of the swinging arm exceeds the recommended dimensions the driveshaft could fail.

 

With ref to item 2 the CDD recomended max drop from the underside of the wheelarch to the centre of the axle is 440mm.

Unfortunatly the wheelarch is not a reliable place to measure from as its position relative to the axle and chassis can vary car to car with size of spacers between body and chassis. When I questioned CDD on this I was told that if you knew the body had extra spacers, for example to aid door alignment then the 440mm could be exceeded by a similar amount. Also with cars set up like mine with shorter stiffer springs and koni dampers on the 3 point fixing brackets the overall movement, up/down of the axle shaft is less than a car with standard softer springs.

Even with shorter stiffer springs like I have the lower position of the swinging arm is determined by the extended length of the tele shock when fitted. It is therefore important that shocks and brackets are bought as a kit for a TR and if the shocks are replaced at a lated date then they need to have the same operating dimensions.

Chris

Edited by potts4a
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Yes Chris, the initial subject Stuart mentioned were the problems with the hub dimentions in relation to the brake drum, as least it was what I understood.

The driveshafts itself is in fact another subject to be watched, and you are right about the swing of the shaft, a critical item.

 

A few weeks a go I looked at a site that showed how to measure the travel in the cv joints from full compression to full extension.

This in fact is what limits the travel of the trailing arm.The upper bump stop should be no problem, but with tele.shocks the lower side might cause problems

For best results you will have to remove the springs and unbolt the tele.shocks, With the shaft bolted up to the diff and the hub left off you will be able to mesure the full travel

The position of the hub in relation to the joint has to be measured in the most upper and lowest position of the trailing arm.

 

It's not rocket science, but it has to be done with care to avoid wrecking the joints at a later stage.

Edited by jean
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Jean,

 

Unbolting the shock absorbers and removing the springs will give the very worst "droop" conditions possible of the rear trailing arms as they extend the CV driveshafts up to and possibly beyond the actual driveshaft operational range. There has been a least a couple of owners on Stags and TRs where the car has been suspended on a lift with the rear wheels left to hang free and completely unsupported without the rear shock absorbers fitted (which are the ONLY restraints against overextension) and the CV driveshafts have been damaged.

I would not carry out a "full droop" exercise WITHOUT the shock absorbers being fitted, they act like the bump stops do in the upward direction by compelling the driveshafts to work ONLY in the range they are engineered to. I'm not sure if by removing the restraining shock absorber and drooping the trailing arms that it may cause the driveshaft joints (large balls in some I've seen) to become unrestrained and damaged if they are not replaced correctly (how would you know with them assembled ?).

Unless the driveshaft supplier gives an exact method for driveshaft full extension testing and measurement I would be wary of applying the test as you have just outlined with a driveshaft connected at both ends.

 

If the vehicle is in use and the trailing arms need to go onto full unrestrained droop in the garage (for rear spring removal etc) then I would unbolt the driveshaft from the flange at the diff and "ease" the driveshaft flange away from it by about 50mm which would allow the driveshaft to be pulled down by wheel hub without overextending it where you can carry out your work safely on spring removal or whatever before connecting the driveshaft back up.

 

Mick Richards

Edited by Motorsport Mickey
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Very correct Mick, Unfortunately my wife was waiting with dinner and it would not have been wise to delay her.... :blink:

 

If not I could have said that the drop of the trailing arm has to be done WITHOUT the hub being fitted.

In the middle and at both ends of the travel the hub has to be inserted into the splines up to the back plate.

With the nut loosely fitted you have to measure the threat sticking out of the hub.

The number measured will show you how far the up and down movement is in acceptable limits. The number is indicated, but I don't remember

Before fitting the shafts I was looking how to fit eventually additional bump stops to limit the downwards travel, I have Konis on my car and don't know how much load they can take.

 

You are right and my apologies for not having finished my text.. :(

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No problem Jean, I often "transgress" with my wife and I still bear the "scars" :o if late for dinner, lol.

 

Mick Richards

 

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  • 1 month later...

Hi,

 

We have measured these accurately, and the difference is actually 15thou. What everyone seems to forget is that 99% of the original rear hubs have been refaced (sometimes more than once) and so unless you measure against an original hub you ARE going to see quite a difference. We have fitted quite a few of these without any issues.

 

TRGB

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Good point, I've not heard of an original unskimmed hub on it's outside wheel carrying flange being available to compare. However the new hub itself on the inside is still 32 thou thicker when measured and that would not have been skimmed.

 

Mick Richards

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